Various types of apparatus for seabed exploration have been proposed to develop seabed resources or investigate seabed environment and most of them have a remotely operated vehicle, while most apparatuses for seabed exploration used for deep sea use unmanned remotely operated vehicle.
Manned remotely operated vehicles require a relatively large amount of manufacturing and operational cost and have a danger of causing human safety accidents, as compared with unmanned remotely operated vehicles.
Various types of unmanned remotely operated vehicles are recently used to explore the seabed and establish and develop seabed facilities for those reasons.
The unmanned remotely operated vehicles have a large difference in manufacturing and operational cost, in accordance with the types of cables connected with the ship (mother ship of the remotely operated vehicles).
When the ship and the unmanned remotely operated vehicle are connected by a communication cable, communication is possible between the ship and the unmanned remotely operated vehicle, such that underwater works become convenient.
However, a relatively large amount of cost is required, because a device for the communication between the ship and the unmanned remotely operated vehicle under the sea is required.
Further, the ship requires to be equipped with measuring device for remote control of investigation measuring device mounted in the unmanned remotely operated vehicle and the remote control measuring device is installed, such that there is a problem in that the working space becomes narrow.
When a cable, not the communication cable, is connected between the ship and the unmanned remotely operated vehicle, although communication is impossible between the ship and the unmanned remotely operated vehicle, the cost is very low, which is economically advantageous.
However, since communication is impossible between the unmanned remotely operated vehicle and the ship, it is possible to move the unmanned remotely operated vehicle by moving the ship, but it is impossible to control various devices in the unmanned remotely operated vehicle from the ship, such that there is considerable inconvenience in investigation work and it is difficult to ensure accuracy in the work.
Further, it is difficult to find the accurate position of the unmanned remotely operated vehicle (the latitudinal and longitudinal positions and the underwater depth) from the ship, such that the available field is limited (the unmanned remotely operated vehicle released under the sea is moved away from the released position by various causes, such as the current, such that the released position (latitudinal and longitudinal positions) and the released length of the cable are very different from the position of the unmanned remotely operated vehicle released under the sea (latitudinal and longitudinal positions) and the underwater depth.
In detail, for example, a gas hydrate, which is a pure energy source that may replace the fossil fuel in the twenty-first century, is a solid energy source formed by combining with water under low temperature and high pressure in the permafrost or the deep sea, and is similar in external shape to the dry ice and has a property of being burned by fire, such that it is also called a burning ice (the main component of the gas hydrate is methane gas).
Since methane gas is discharged when there is a gas hydrate described above in the seafloor, it is possible to check whether there is a gas hydrate by releasing an investigation apparatus and measuring the concentration of methane gas under the sea (the methane gas may be discharged to the sea by natural dissociation of the gas hydrate and manmade dissociation (development and production)). Further, the methane gas is also made by activity of submarine volcanoes or dissolution of organic substances near the coast (harbor).
However, it is required to be able to relatively accurately find the accurate position (latitudinal and longitudinal positions and underwater depth) of the investigation device, such as an unmanned remotely operated vehicle released under the sea, from the ship, in order to check whether there is a gas hydrate described above.
This is because it is required to position a device measuring the concentration of the methane gas, such as methane gas measuring device, close to the seafloor (at 1 m˜2 m above from the seafloor) in order to find there is a gas hydrate, for ensuring accuracy.
However, since it is impossible to find the position (latitudinal and longitudinal positions and underwater depth) of the unmanned remotely operated vehicle released under the sea by a cable, from the ship, it is impossible to investigate whether there is a gas hydrate through the cable.
On the other hand, the unmanned remotely operated vehicle released under the sea by the cable is not equipped with a device that collects seabed sediments, such that it is impossible to collect seabed sediments.